Pyrolyzed coal finisher, coal upgrade plant, and method for manufacturing deactivated pyrolyzed coal

ABSTRACT

To provide a pyrolyzed coal finisher capable of deactivating pyrolyzed coal within a short time without causing a cost increase. A pyrolyzed coal finisher includes: a mixer  86  that forms slurry by mixing particulate pyrolyzed coal that is pyrolyzed coal into a chemical solution having an oxygen blocking function after being solidified; and a belt filter device  88  that filters the slurry formed in the mixer  86  in a state in which each particle of the pyrolyzed coal is coated with the chemical solution. The pyrolyzed coal finisher further includes a chemical solution circulation path  94  that guides the chemical solution separated from the pyrolyzed coal by the belt filter device  88  to the mixer  86.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a pyrolyzed coal finisher which deactivates pyrolyzed coal so as to avoid spontaneous combustion, a coal upgrade plant, and a method for manufacturing deactivated pyrolyzed coal.

2. Description of Related Art

Since low ranking coal such as sub-bituminous coal and lignite has a lower carbonization degree and a higher water content than high ranking coal, a calorific value per unit weight is lower. However, since there are abundant deposits of low ranking coal, the low ranking coal is desired to be effectively used. Thus, various coal upgrading techniques have been studied in which the calorific value of the low ranking coal is increased by performing pyrolysis after drying the low ranking coal, and upgraded coal is deactivated so as to prevent spontaneous combustion during transportation or storage (e.g., Japanese Unexamined Patent Application, Publication No. 2014-31462 (hereinafter referred to as JPA 2014-31462) and PCT International Publication No. WO 2013/103097 (hereinafter referred to as WO 2013/103097)).

JPA 2014-31462 and WO 2013/103097 disclose that pyrolyzed coal after pyrolysis is cooled, and oxygen is then brought into contact with the pyrolyzed coal to oxidize the pyrolyzed coal and thereby deactivate the surface of the pyrolyzed coal.

However, it is necessary to gradually perform the oxidation by slowing down an oxidation rate in order to avoid the spontaneous combustion of the pyrolyzed coal caused by rapid oxidation. Thus, it takes an enormous amount of time to perform the deactivating process.

Each of JPA 2014-31462 and WO 2013/103097 also discloses that particles of the pyrolyzed coal are gathered and molded (briquetted) into a predetermined shape so as to reduce the surface area, and the deactivating process is performed.

However, a briquetter for briquetting the pyrolyzed coal is required, which is one of the causes for a cost increase.

The present invention has been made in view of such circumstances, and an object thereof is to provide a pyrolyzed coal finisher, a coal upgrade plant, and a method for manufacturing deactivated pyrolyzed coal capable of deactivating pyrolyzed coal within a short time without causing a cost increase.

BRIEF SUMMARY OF THE INVENTION

To achieve the above object, a pyrolyzed coal finisher, a coal upgrade plant, and a method for manufacturing deactivated pyrolyzed coal of the present invention employ the following solutions.

A pyrolyzed coal finisher according to one aspect of the present invention includes: a mixer that forms slurry by mixing particulate pyrolyzed coal that is pyrolyzed coal into a chemical solution having an oxygen blocking function after being solidified; and a filter that filters the slurry formed in the mixer in a state in which each particle of the pyrolyzed coal is coated with the chemical solution.

By forming the slurry of the chemical solution having the oxygen blocking function after being solidified and the particulate pyrolyzed coal, and filtering the slurry by the filter to coat each particle of the pyrolyzed coal with the chemical solution, deactivated pyrolyzed coal, each particle of which is entirely coated with an oxygen blocking film, can be obtained. As described above, by filtering the slurry by the filter, the deactivated pyrolyzed coal evenly coated with the oxygen blocking film can be mass-manufactured.

The deactivation of the pyrolyzed coal can be achieved by coating the pyrolyzed coal with the chemical solution having the oxygen blocking function. Thus, a deactivating equipment that oxidizes the pyrolyzed coal gradually from the surface over time by bringing the pyrolyzed coal into contact with oxygen or air as in conventional cases is not required, so that the length of time required for treatment and the costs can be reduced.

Since each particle of the pyrolyzed coal can be deactivated, a briquetter that gathers the particulate pyrolyzed coal and molds (briquettes) the pyrolyzed coal so as to reduce the surface area is not required. Thus, the length of time required for treatment and the costs can be reduced. Since the entire surface of each particle is coated with the oxygen blocking film, the deactivation can be more surely achieved than using a deactivating method of briquetting the particulate pyrolyzed coal so as to reduce the surface area.

A chemical solution obtained by dissolving a polymer such as polyethylene oxide and starch in a solvent such as water is used as the chemical solution having the oxygen blocking function after being solidified. It is preferable to use a chemical solution that is solidified at a normal temperature.

For example, the particles of the pyrolyzed coal have a particle size of about 0.5 to 5.0 mm.

The pyrolyzed coal finisher according to one aspect of the present invention further includes a chemical solution circulation path that guides the chemical solution separated from the pyrolyzed coal by the filter to the mixer.

Since the chemical solution separated from the pyrolyzed coal by the filter is returned to the mixer to be reused, the used amount of the chemical solution can be reduced.

In the pyrolyzed coal finisher according to one aspect of the present invention, the filter is a belt filter.

Since the belt filter is used as the filter, continuous treatment is enabled, so that the deactivated pyrolyzed coal can be mass-manufactured.

A coal upgrade plant according to one aspect of the present invention includes: a pyrolyzer that pyrolyzes coal; and the above pyrolyzed coal finisher that deactivates the pyrolyzed coal pyrolyzed by the pyrolyzer.

Since the above pyrolyzed coal finisher is used, deactivated pyrolyzed coal evenly coated with an oxygen blocking film can be obtained.

A method for manufacturing deactivated pyrolyzed coal according to one aspect of the present invention includes: a mixing step of forming slurry by mixing particles of pyrolyzed coal that is pyrolyzed coal into a chemical solution having an oxygen blocking function after being solidified; and a filtering step of filtering the slurry formed in the mixing step in a state in which each particle of the pyrolyzed coal is coated with the chemical solution.

By forming the slurry of the chemical solution having the oxygen blocking function after being solidified and the particles of the pyrolyzed coal, and filtering the slurry by the filter to coat each particle of the pyrolyzed coal with the chemical solution, deactivated pyrolyzed coal, each particle of which is entirely coated with an oxygen blocking film, can be obtained. As described above, by filtering the slurry by the filter, the deactivated pyrolyzed coal evenly coated with the oxygen blocking film can be mass-manufactured.

Since the pyrolyzed coal is deactivated by filtering the slurry of the pyrolyzed coal and the chemical solution having the oxygen blocking function by the filter, the pyrolyzed coal can be deactivated within a short time.

Also, since the deactivation is enabled without using a finisher using oxidation, and a briquetter as in conventional cases, the costs can be reduced.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a schematic configuration diagram illustrating the entire configuration of a coal upgrade plant according to one embodiment of the present invention.

FIG. 2 is a schematic configuration diagram illustrating a finisher shown in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

In the following, one embodiment according to the present invention is described by reference to the drawings.

FIG. 1 shows a coal upgrade plant including a pyrolyzed coal finisher according to one embodiment of the present invention. The coal upgrade plant includes a dryer 1 that heats and dries coal, a pyrolyzer 3 that heats and pyrolyzes the dried coal dried in the dryer 1, a quencher 5 that cools the pyrolyzed coal pyrolyzed in the pyrolyzer 3, and a pyrolyzed coal finisher (simply referred to as “finisher” below) 7 that deactivates the pyrolyzed coal cooled in the quencher 5.

A coal hopper 12 that receives raw coal 10 is provided on the upstream side of the dryer 1. The raw coal is low ranking coal such as sub-bituminous coal and lignite, and has a water content of 25 wt % or more to 60 wt % or less. The coal guided from the coal hopper 12 is crushed to a particle size of, for example, about 20 mm or less in a crusher 14.

The coal crushed in the crusher 14 is guided to the dryer 1. The dryer 1 is of indirect heating type using steam, and includes a cylindrical vessel 16 that rotates about a center axis, and a plurality of heating tubes 18 that are inserted into the cylindrical vessel 16. The coal guided from the crusher 14 is fed into the cylindrical vessel 16. The coal fed into the cylindrical vessel 16 is guided from one end side (the left side in FIG. 1) to the other end side while being agitated according to the rotation of the cylindrical vessel 16. Steam having a temperature of 150° C. or more to 200° C. or less (more specifically, 180° C.), which is produced in a steam system 20, is fed into each of the heating tubes 18, thereby indirectly heating the coal in contact with the outer periphery of each of the heating tubes 18. The steam fed into each of the heating tubes 18 is condensed after applying condensation heat by heating the coal, discharged from the dryer 1, and returned to the steam system 20.

A carrier gas is fed into the cylindrical vessel 16 through a carrier gas circulation path 22. As the carrier gas, an inert gas is used. More specifically, a nitrogen gas is used. When in shortage, the nitrogen gas is additionally fed from a nitrogen feed path 24 that is connected to the carrier gas circulation path 22. The carrier gas is discharged outside of the cylindrical vessel 16 through a carrier gas discharge path 26 that is connected to the cylindrical vessel 16 while catching a desorbed component (steam, pulverized coal, mercury, mercury-based substances, etc.) desorbed from the coal when passing through the cylindrical vessel 16.

A cyclone (dust collector) 28, a carrier gas cooler 30, and a scrubber 32 are provided in the carrier gas discharge path 26 sequentially from the upstream side of a carrier gas flow direction.

The cyclone 28 mainly removes the pulverized coal (for example, having a particle size of 100 μm or less) that is a solid from the carrier gas by use of a centrifugal force. The pulverized coal removed in the cyclone 28 is guided to the upstream side of a bag filter 34 as indicated by reference character A. The pulverized coal separated in the cyclone 28 may be also mixed into the dried coal dried in the dryer 1.

The carrier gas cooler 30 cools the carrier gas, from which the pulverized coal has been removed, thereby condensing steam guided together with the carrier gas and removing the condensed steam as drain water. The carrier gas cooler 30 is an indirect heat exchanger. Industrial water having a normal temperature is used as a cooling medium. Recycled water separated in a waste water treatment equipment 40 may be also used as the cooling medium. The drain water produced in the carrier gas cooler 30 is guided to a liquid phase section in a lower portion of the scrubber 32.

The scrubber 32 removes the mercury and/or the mercury-based substances (simply referred to as “mercury etc.” below) from the carrier gas, from which the pulverized coal and the steam have been removed. Water is used as an absorber used in the scrubber 32. More specifically, the recycled water separated in the waste water treatment equipment 40 is used. The mercury etc. in the carrier gas is adsorbed by the water sprayed from above the scrubber 32, and guided to the liquid phase section in the lower portion of the scrubber 32. In the scrubber 32, the pulverized coal that could not be removed in the cyclone 28 is also removed.

An upstream end of the carrier gas circulation path 22 is connected to an upper portion of the scrubber 32. A blower 36 is provided at an intermediate position of the carrier gas circulation path 22. The carrier gas treated in the scrubber 32 is returned to the dryer 1 by the blower 36. Although not shown in the drawings, one portion of the carrier gas treated in the scrubber 32 is guided to a combustor 42.

The waste water treatment equipment 40 is connected to the lower portion of the scrubber 32 through a waste water path 38. The waste water treatment equipment 40 separates sludge 39, which is a solid content such as the pulverized coal and the mercury etc., and the recycled water by a sedimentation tank (not shown) after aggregating and enlarging the mercury etc. by injecting a chelating agent into waste water. The recycled water is reused in various portions of the plant.

The coal (dried coal) dried in the dryer 1 passes through a dried coal feed path 44 to be guided to the pyrolyzer 3 by use of its weight. The pyrolyzer 3 is an external-heat rotary kiln, and includes a rotating inner cylinder 46, and an outer cylinder 48 that covers the outer peripheral side of the rotating inner cylinder 46. A nitrogen gas as a carrier gas is fed into the rotating inner cylinder 46.

A combustion gas produced in the combustor 42 is guided to a space between the rotating inner cylinder 46 and the outer cylinder 48 through a combustion gas introduction path 50. Accordingly, the inside of the rotating inner cylinder 46 is maintained at 350° C. or more to 450° C. or less (for example, 400° C.)

To the combustor 42, an air feed path 54 that guides combustion air force-fed by a blower 52 into the combustor, a natural gas feed path 55 that guides a natural gas as fuel into the combustor, and a pyrolysis gas collection path 56 that collects a pyrolysis gas generated in the pyrolyzer 3 together with the carrier gas, and guides the gas into the combustor are connected. In the combustor 42, a fire 51 is formed by the natural gas, the pyrolysis gas, and the air fed into the combustor. Since the pyrolysis gas contains a volatile content such as tar and has a predetermined calorific value, the pyrolysis gas is used as fuel in the combustor 42. The natural gas fed from the natural gas feed path 55 is used for adjusting a calorific value of the fuel injected into the combustor 42. A flow rate of the natural gas is adjusted such that the combustion gas produced in the combustor 42 has a desired temperature.

A pyrolysis gas discharge path 58 that is used in emergency is connected to an intermediate position of the pyrolysis gas collection path 56. A flare stack 60 is installed on the downstream side of the pyrolysis gas discharge path 58. A combustible component such as tar in the pyrolysis gas is incinerated by the flare stack 60, and a gas obtained after the incineration is released to the atmosphere.

A combustion gas discharge path 62 through which the combustion gas produced in the combustor is discharged is connected to the combustor 42. An upstream end of the combustion gas introduction path 50 that guides the combustion gas to the pyrolyzer 3 is connected to an intermediate position of the combustion gas discharge path 62. A first medium-pressure boiler 64 is provided in the combustion gas discharge path 62 on the downstream side of a connection position with the combustion gas introduction path 50.

An after-heating gas discharge path 66 through which the combustion gas after heating the rotating inner cylinder 46 is discharged is connected to the outer cylinder 48 of the pyrolyzer 3. A second medium-pressure boiler 68 is provided in the after-heating gas discharge path 66. The after-heating gas discharge path 66 is connected to the combustion gas discharge path 62 on the downstream side. A blower 70 that force-feeds the combustion gas is provided in the combustion gas discharge path 62 on the downstream side of a connection position with the after-heating gas discharge path 66.

The downstream side of the combustion gas discharge path 62 is connected to the bag filter 34. A flue gas, from which combustion ash or the like is removed in the bag filter 34, is released to the atmosphere (ATM).

The steam system 20 includes the first medium-pressure boiler 64 and the second medium-pressure boiler 68. In the second medium-pressure boiler 68, boiler feed water (BFW) fed thereto is heated by the combustion gas flowing through the after-heating gas discharge path 66, thereby producing steam. In the first medium-pressure boiler 64, the steam produced in the second medium-pressure boiler 68 is guided, and heated by the flue gas flowing through the combustion gas discharge path 62, thereby producing steam having a higher pressure. Medium-pressure steam produced in the first medium-pressure boiler 64 and medium-pressure steam produced in the second medium-pressure boiler 68 are respectively stored in a steam drum (not shown), and fed to various portions of the plant such as the heating tubes 18 of the dryer 1.

The pyrolyzed coal pyrolyzed in the pyrolyzer 3 is guided to the quencher 5 through a pyrolyzed coal feed path 72 by use of gravity. The quencher 5 includes a first cooler 74 that receives the pyrolyzed coal from the pyrolyzer 3, and a second cooler 76 that receives the pyrolyzed coal cooled by the first cooler 74.

The first cooler 74 is a shell-and-tube heat exchanger, and includes a first cylindrical vessel 78 that rotates about a center axis, a first water spray tube 79 that is inserted into the first cylindrical vessel 78, and a plurality of first cooling tubes 80 that are inserted into the first cylindrical vessel 78. The first water spray tube 79 is installed in a stationary state with respect to the rotating first cylindrical vessel 78. The pyrolyzed coal having a temperature of 300° C. or more to 500° C. or less (for example, about 400° C.), which is guided from the pyrolyzer 3, is fed into the first cylindrical vessel 78. The pyrolyzed coal fed into the first cylindrical vessel 78 is guided from one end side (the left side in FIG. 1) to the other end side while being agitated according to the rotation of the first cylindrical vessel 78.

Industrial water having a normal temperature is guided to the first water spray tube 79. The water is sprayed on the pyrolyzed coal and thereby brought into direct contact with the pyrolyzed coal to cool down the pyrolyzed coal. The first water spray tube 79 is provided on the upstream side (the left side in FIG. 1) of the pyrolyzed coal moving within the first cylindrical vessel 78. The recycled water separated in the waste water treatment equipment 40 may be used as the water fed to the first water spray tube 79.

Boiler feed water having a temperature of 50° C. or more to 100° C. or less (for example, about 60° C.) is fed into each of the first cooling tubes 80, thereby indirectly cooling the pyrolyzed coal in contact with the outer periphery of each of the first cooling tubes 80. Each of the first cooling tubes 80 is provided on the downstream side (the right side in FIG. 1) of the pyrolyzed coal moving within the first cylindrical vessel 78. Each of the first cooling tubes 80 cools the pyrolyzed coal cooled by the first water spray tube 79 to about 150° C. that is equal to or higher than a condensation temperature of water.

The second cooler 76 has substantially the same configuration as the first cooler 74. The second cooler 76 is a shell-and-tube heat exchanger, and includes a second cylindrical vessel 81 that rotates about a center axis, a second water spray tube 82 that is inserted into the second cylindrical vessel 81, and a plurality of second cooling tubes 83 that are inserted into the second cylindrical vessel 81. The second water spray tube 82 is installed in a stationary state with respect to the rotating second cylindrical vessel 81. The pyrolyzed coal cooled to about 150° C. in the first cooler 74 is fed into the second cylindrical vessel 81. The pyrolyzed coal fed into the second cylindrical vessel 81 is guided from one end side (the left side in FIG. 1) to the other end side while being agitated according to the rotation of the second cylindrical vessel 81.

Industrial water having a normal temperature is guided to the second water spray tube 82. The water is sprayed on the pyrolyzed coal to adjust the water content of the pyrolyzed coal to a desired value (for example, 8 wt %). The second water spray tube 82 is provided over substantially the entire second cylindrical vessel 81 in an axial direction. The recycled water separated in the waste water treatment equipment 40 may be used as the water fed to the second water spray tube 82.

Industrial water having a normal temperature is guided into each of the second cooling tubes 83, thereby indirectly cooling the pyrolyzed coal in contact with the outer periphery of each of the second cooling tubes 83. Each of the second cooling tubes 83 cools the pyrolyzed coal to about 50° C. The recycled water separated in the waste water treatment equipment 40 may be used as the water fed to each of the second cooling tubes 83.

The pyrolyzed coal cooled in the quencher 5 is guided to the finisher 7 through a cooled pyrolyzed coal feed path 84.

As shown in FIG. 2, the finisher 7 includes a mixer 86 and a belt filter device 88.

The pyrolyzed coal guided from the quencher 5, and a chemical solution for performing a deactivating process are guided to the mixer 86. The mixer 86 mixes the pyrolyzed coal and the chemical solution by a kneader (not shown) to form slurry of the pyrolyzed coal and the chemical solution.

The pyrolyzed coal guided to the mixer 86 has a particulate form, and has a particle size of about 0.5 to 5.0 mm.

The chemical solution has an oxygen blocking function after being solidified. For example, a chemical solution obtained by dissolving a polymer such as polyethylene oxide and starch in a solvent such as water is used. It is preferable to use a chemical solution, such as polyethylene oxide and starch, which is solidified at a normal temperature.

The belt filter device 88 includes an endless belt filter 90 where a mesh-like filter section is formed over substantially the entire belt surface, and a pair of rollers 92 where the belt filter 90 is wound. The belt filter 90 has a mesh small enough not to pass the particulate pyrolyzed coal having a particle size of, for example, about 1 mm. A drive device (not shown) is provided in the rollers 92. The rollers 92 are rotated about axes as indicated by arrows in the drawing by the power of the drive device.

Although not shown in the drawings, a press that presses the belt filter 90 from above or a suction device that sucks the belt filter 90 from below while the belt filter 90 is running substantially in a horizontal direction between upper ends of the rollers 92 is provided. The slurry fed from the mixer 86 to one upper end (the left side in the drawing) of the belt filter 90 through a slurry feed path 87 is filtered by the press or the suction device described above while being transferred to the other end side along with the belt filter 90 running substantially in the horizontal direction. Accordingly, the slurry is separated into the particulate pyrolyzed coal coated with the chemical solution over the entire surface, and the chemical solution after passing through the belt filter 90.

The coated particulate pyrolyzed coal separated by the belt filter 90 is removed from the belt filter 90 by a scraper or the like (not shown). The chemical solution is solidified at a normal temperature, so that an oxygen blocking film is formed over the entire surface of each particle. Deactivated pyrolyzed coal, i.e., final upgraded coal 104 is thereby obtained.

The chemical solution separated by the belt filter 90 is collected from a lower portion, and transferred to the mixer 86 again through a chemical solution circulation path 94.

The following effects are produced by the present embodiment.

By forming the slurry of the chemical solution having the oxygen blocking function after being solidified and the particulate pyrolyzed coal, and filtering the slurry by the belt filter 90 to coat each particle of the particulate pyrolyzed coal with the chemical solution, the deactivated pyrolyzed coal, each particle of which is entirely coated with the oxygen blocking film, can be obtained. As described above, by filtering the slurry by the belt filter 90, the deactivated pyrolyzed coal evenly coated with the oxygen blocking film can be mass-manufactured.

Also, the deactivation of the pyrolyzed coal can be achieved by coating the pyrolyzed coal with the chemical solution having the oxygen blocking function. Thus, a deactivating equipment that oxidizes the pyrolyzed coal gradually from the surface over time by bringing the pyrolyzed coal into contact with oxygen or air as in conventional cases is not required, so that the length of time required for treatment and the costs can be reduced.

Since each particle of the particulate pyrolyzed coal can be deactivated, a briquetter that gathers the particulate pyrolyzed coal and molds (briquettes) the pyrolyzed coal so as to reduce the surface area is not required. Thus, the length of time required for treatment and the costs can be reduced. Since the entire surface of each particle is coated with the oxygen blocking film, the deactivation can be more surely achieved than using a deactivating method of briquetting the particulate pyrolyzed coal so as to reduce the surface area.

Since the chemical solution separated from the pyrolyzed coal by the belt filter device 88 is returned to the mixer 86 through the chemical solution circulation path 94 to be reused, the used amount of the chemical solution can be reduced.

Since the belt filter 90 is used, continuous treatment is enabled, so that the deactivated pyrolyzed coal can be mass-manufactured.

-   1 Dryer -   3 Pyrolyzer -   5 Quencher -   7 Finisher -   9 Briquetter -   10 Raw coal -   12 Coal hopper -   14 Crusher -   16 Cylindrical vessel -   18 Heating tube -   20 Steam system -   22 Carrier gas circulation path -   28 Cyclone -   30 Carrier gas cooler -   32 Scrubber -   34 Bag filter -   40 Waste water treatment equipment -   42 Combustor -   46 Rotating inner cylinder -   48 Outer cylinder -   50 Combustion gas introduction path -   74 First cooler -   76 Second cooler -   78 First cylindrical vessel -   79 First water spray tube -   80 First cooling tube -   81 Second cylindrical vessel -   82 Second water spray tube -   83 Second cooling tube -   86 Mixer -   87 Slurry feed path -   88 Belt filter device -   90 Belt filter -   92 Roller -   94 Chemical solution circulation path -   104 Upgraded coal 

What is claimed is:
 1. A pyrolyzed coal finisher comprising: a mixer for forming slurry by mixing particulate pyrolyzed coal that is pyrolyzed coal into a chemical solution having an oxygen blocking function after being solidified; and a filter for filtering the slurry formed in the mixer in a state in which each particle of the pyrolyzed coal is coated with the chemical solution.
 2. The pyrolyzed coal finisher according to claim 1, further comprising a chemical solution circulation path for guiding the chemical solution separated from the pyrolyzed coal by the filter to the mixer.
 3. The pyrolyzed coal finisher according to claim 1, wherein the filter is a belt filter.
 4. A coal upgrade plant comprising: a pyrolyzer for pyrolyzing coal; and a pyrolyzed coal finisher according to claim 1 that deactivates the pyrolyzed coal pyrolyzed by the pyrolyzer.
 5. A method for manufacturing deactivated pyrolyzed coal comprising: a mixing step of forming slurry by mixing particles of pyrolyzed coal that is pyrolyzed coal into a chemical solution having an oxygen blocking function after being solidified; and a filtering step of filtering the slurry formed in the mixing step in a state in which each particle of the pyrolyzed coal is coated with the chemical solution. 